The present invention pertains to particular mixtures of vegetable oils having a reduced tendency to produce objectionable odors when heated to frying temperatures, especially after prolonged storage and which have an improved flavor on storage.
Generally, vegetable oils intended to be used for cooking or other food preparation purposes, are processed by subjecting them to the well known processes of alkali refining, earth bleaching and steam deodorization. Refining and bleaching are described in detail in Chapter 4 of Volume 2 of Baileys Industrial Oil and Fat Products, Wiley-Interscience Publishers (1982), incorporated by reference herein. Deodorization is described in detail in Chapter 3 of Volume 3 of Baileys Industrial Oil and Fat Products, Wiley-Interscience Publishers (1985), incorporated by reference herein. When treated in this manner, the fresh oil has a relatively bland odor at room temperature and a very light color.
Notwithstanding these treatments, however, when the oils (especially soybean oil and canola oil) are subjected to frying temperatures, they produce odors in the area surrounding the site of cooking. These odors are generally objectionable, and are variously described as "painty", "beany", "grassy", "fishy", "acrid", etc.
This odor is believed to be caused by the oxidation of the polyunsaturated fatty acids present in these oils, in particular linolenic and linolenic acids. Low molecular weight aldehydes, ketones, fatty acids and hydrocarbon are formed. Some of these have acrid, fishy and other disagreeable aromas.
A commonly used means of reducing the tendency of refined vegetable oils to produce objectionable odors when heated to frying temperatures is partial hydrogenation. However, the hydrogenation process must be carefully controlled to prevent the resulting oil from obtaining a lard-like consistency. Hydrogenation increases the saturation of fatty acids in the oil, which many nutritionists believe causes a reduction in the nutritional value of the oil. The number of trans fatty acids increases when the oil is hydrogenated. Saturated fats have been associated by many identical experts with increased risk of heart disease. Hydrogenation has an economic disadvantage because stearin is produced in the oil, which must be removed if the oil is to remain clear when shipped or stored in cool environments.
U.S. Pat. No. 3,758,532, Gibble, issued Sep. 11, 1973 discloses a process for treating soybean oil to improve its odor during storage and drying. In that process the refined oil is degassed, then gassed with carbon dioxide and then heated in the presence of copper chromite under a carbon dioxide atmosphere. The use of carbon dioxide and copper chromite adds to the cost of processing the oil.
The blending of vegetable oils for economic reasons and/or to obtain specific averaged physical properties or fatty acid compositions is well known. U.S. Pat. No. 4,568,556, McCoy, issued Feb. 4, 1986 discloses the use of individual oils and mixtures thereof as the "soft oil" in margarines. Preferred oils are safflower oil, sunflower oil, soybean oil and mixtures thereof. U.S. Pat. No. 3,186,854, Going, issued Jun. 1, 1965 discloses the use of mixtures of various oils and crystal inhibitors to obtain salad oils which remain clear when stored at low temperatures.
U.S. Pat. No. 3,529,974, Melnick et al., issued Sep. 22, 1970 discloses a blend of oils intended to achieve the fatty acid composition, nutritional value and physical properties of corn oil. The oil blend comprises 40-45% refined/bleached sunflower oil, 20-25% refined/bleached/hydrogenated/winterized soybean oil, 15-70% refined/bleached/winterized cottonseed oil and 3-8% refined/bleached peanut oil. The mixture of oils is deodorized after blending.
EPO publication 411,681 (1991, Procter & Gamble) relates to cooking oil compositions having a low odor producing tendency upon heating. The mixture comprises refined, bleached and deodorized sunflower seed oil, refined, bleached and deodorized soybean oil blended with refined, bleached and deodorized canola oil. The ratio of sunflower to soybean is 20:80 to 70:30.
Prevot et al., JAOCS, 67, No. 3, pages 161-164 (1990) describes the room aroma of low-linolenic rapeseed oil. This article describes the characteristic odor of sunflower as "fruity".
EPO patent application 296,177 assigned Warner Lambert (1988) describes the use of an oil soluble sensory masking agent to produce a taste masking and/or odor masking sensation for unpleasant edible oils. The masking agent is present at a level of 0.1-10%. Materials which can be used include anethole, eugenol, vanilla, and natural or artificial fruit oils, including citris and mint oils. Citrus oils are said to produce an especially pleasant tasting and pleasant smelling composition.
SU 1,479,494 (1989) describes deep drying fats to which pinene is added (0.015 to 0.017%) as an antioxidant. The fats are protected from thermal damage.
Japanese patent application 60/078, 542 (1985, Nikken Stamy) describes an edible oil blend which has a balanced fatty acid composition. Oils which can be blended include soybean oil, rapeseed oil and sunflower oil.
Japanese application 58/184,635 (1985, Nitsuken Sutamii) discloses a way to make food oils having a balanced fatty acid content. The food oil is prepared by mixing corn oil or rice oil with other oils including rapeseed and sunflower seed oil.
Abstract KK-5, JAOCS, 65, No. 4, pages 528-29 (Apr., 1988) discloses the relative flavor and oxidative stability of canola oil blends with cottonseed or sunflower seed oil. Heat accelerated oxidation was reduced when canola is blended with sunflower oil.
King, et al., "Cottonseed Oil as a Frying Medium", JAOCS, 66 (No. 2) 192-195 (1989) found that high oleic sunflower oils produced much less room aroma hen heated. Japan 59/154,973 (1983, Gakko Hojin) discloses that a monoterpene and monoterpene alcohol ester have a powerful synergistic effect as antioxidants when combined with tocopherol in fats or oils.
U.S. Pat. No. 4,806,374 (Lever, 1989) uses silicones with the linalool and linalyl acetates to make better smelling frying fats. GB, 1,200,450 (Lever, 1970) discloses frying fats in which citrus oils are added at the level of 100-1000 parts per million to reduce the development of unpleasant room odors when the oil is used for frying. Similar results can be achieved by using other essential oils.
U.S. Pat. No. 3,460,948 issued to Linteris et al. (Lever, 1969) discloses glyceride oils for frying food containing citrus oils to reduce the offensive cooking odors. From 100-1000 parts per million of the citrus oil are used.
It is the object of the present invention to provide refined, bleached and deodorized cooking oils which have a reduced tendency to produce objectionable odors when heated to frying temperatures, without the necessity of subjecting the oils to additional processing, or adding non-vegetable oil ingredients to the oil by blending refined, bleached but undeodorized sunflower seed oil with the unsaturated cooking oil. This sunflower seed oil contains terpenes and other odor producing compounds which effectively mask the malodors of the cooking oil and improve its flavor on aging.